1. Field of the Invention
Exemplary aspects of the present invention generally relate to an image forming apparatus including a sheet feed cassette, a form of which is changeable to accommodate recording media in a variety of sizes.
2. Description of the Related Art
In image forming apparatuses such as printers, copiers, plotters, facsimile machines, and multifunction devices having two or more of printing, copying, plotting, and facsimile functions, recording media are generally supplied from a sheet feed cassette attached to the image forming apparatus.
In order to achieve user-friendliness, it is desirable that the image forming apparatus have a front-access configuration in which both supply of the recording media and retrieval of recording media having images thereon are performed by a user from the front side of the apparatus. Therefore, regardless of the type of system employed in the image forming apparatus, whether an electrophotographic system or an inkjet recording system, the sheet feed cassette that holds a stack of recording media is generally disposed to a lower portion of the image forming apparatus so that the recording media can be supplied from the front side of the apparatus. During image formation, a recording medium fed from the sheet feed cassette is conveyed to an image forming part to form an image on the recording medium. The recording medium having the image thereon is then discharged to an internal discharge tray or a discharge tray provided to an upper front portion of the apparatus and is retrieved by the user from the front side of the apparatus.
In an inkjet-type image forming apparatus, recording media fed from the sheet feed cassette often make a U-turn during image formation and are discharged from the image forming apparatus with a side having an image thereon facing up. Such a configuration makes the image forming apparatus more compact, and secures time to dry out ink on the recording media after image formation, thereby preventing adherence of ink to the discharge tray. Although the recording media discharged from the image forming apparatus are stacked on the discharge tray in reverse order when images are formed on multiple recording media consecutively, such a problem can be often solved using software now. The multiple recording media consecutively discharged from the image forming apparatus may be more easily stacked on the discharge tray in the proper order by making a U-turn twice during image formation so as to be discharged with the side having the image thereon facing down. However, such a configuration increases the height of the image forming apparatus. In particular, the less-frequent use of image forming apparatuses in small offices or by consumers prioritizes reduction of installation space of the apparatuses. Thus, compactness and inexpensiveness of the image forming apparatuses are in greater demand.
In order to handle recording media in a variety of sizes, the sheet feed cassette of a compact image forming apparatus is configured to be extendable so that even large-sized recording media can be accommodated in the sheet feed cassette. As a result, the sheet feed cassette is sometimes protruding from the image forming apparatus when being extended. Meanwhile, when not in use or holding small-sized recording media, the sheet feed cassette is contracted to be flush with the side of the image forming apparatus. The extendable sheet feed cassette is well known and often employed in the image forming apparatuses.
In some related-art extendable sheet feed cassettes, an opening of the sheet feed cassette from which the recording media are supplied is exposed to the outside of the image forming apparatus, allowing entrance of dust within the image forming apparatus and dampness on the recording media placed within the sheet feed cassette. Dust often causes various problems in the image forming apparatuses and the damp recording media may cause irregular image formation. In order to prevent these, it is conceivable that the sheet feed cassette is accommodated within the image forming apparatus. However, the compactness of contemporary image forming apparatuses sometimes prevents accommodation of the sheet feed cassette that can handle large-sized recording media within the image forming apparatus.
For the above reason, the opening of the sheet feed cassette is often covered with a cassette cover attached to the sheet feed cassette. However, attachment of the cassette cover only when the sheet feed cassette is extended burdens the user. In the worst case, the cassette cover may be lost and the opening of the sheet feed cassette may be uncovered, resulting in irregular images caused by dust entering the image forming apparatus and the damp recording media.
In the previously-described image forming apparatus in which the recording medium fed from the sheet feed cassette makes a U-turn during image formation so as to be discharged with the side having the image thereon facing up, the sheet feed cassette and the discharge tray are often disposed close to each other due to the compact structure of the image forming apparatus. Taking advantage of the close proximity of the sheet feed cassette to the discharge tray, an extendable cassette cover is accommodated within the discharge tray so that the cassette cover is withdrawn from the discharge tray to cover the opening of the sheet feed cassette when the sheet feed cassette is extended. However, the cassette cover withdrawn from the discharge tray fixed to the image forming apparatus hinders removal of a jammed recording medium from a portion of the sheet feed cassette in which the recording medium is picked up. In addition, the discharge tray also often needs to be extended to handle recording media in a variety of sizes due to compactness of the image forming apparatus. Improper operation of the extendable discharge tray may cause irregular stacking of the recording media on the discharge tray. Consequently, the recording media discharged from the image forming apparatus may drop off from the discharge tray or may not be sequentially stacked on the discharge tray in the proper order.
Thus, upon change of the size of the recording media held by the sheet feed cassette, not only the sheet feed cassette but sometimes also the cassette cover need to be detached from and reattached to the image forming apparatus when the sheet feed cassette is extended or contracted to accommodate the recording media. Further, the discharge tray also needs to be extended or contracted, thereby inconveniencing the user and possibly causing improper setting of the sheet feed cassette, the cassette cover, or the discharge tray.
In order to prevent deformation, damage, or jam of recording media caused by improper operation of the extendable sheet feed cassette, JP-2010-006592-A proposes a configuration in which a sheet feed cassette and a discharge tray are integrally extendable and a member that restricts contraction of the sheet feed cassette while the sheet feed cassette is attached to the image forming apparatus is provided. However, provision of such a member increases production costs.
In another approach (JP-H07-133050-A), a state of the discharge tray is changeable in conjunction with extension and contraction of the sheet feed cassette, such that an auxiliary discharge tray can be used depending on the size of recording media in a compact image forming apparatus. However, this approach complicates the configuration of the image forming apparatus and also increases production costs.